116 THE ROYAL SOCIETY OF CANADA 



frogs — due perhaps to adaptation — sufficient to permit the tissues of 

 the latter to survive a temperature several or many degrees below that 

 fatal to the former. This assumption, which would apparently suggest 

 considerable chemical difference in the structure of the protoplasm, 

 seems to us very unlikely. Although there is evidence that differences 

 may exist between frogs from vastly different climates (we know 

 however of no data bearing on the death temperature of the tissues of 

 frogs from tropical climates) the extreme temperatures of the two 

 districts concerned are not so markedly different as to warrant this 

 assumption. 



We are therefore of the opinion that, until definite scientific data 

 can be adduced, there is no evidence for belief in statements that frozen 

 frogs have been found at temperature lower than -2°C., which subse- 

 quently recovered. It must be borne in mind that even above this 

 temperature long exposure will cause total solidification and every 

 appearance of death, and that frogs found several feet below the surface 

 of the ground may, at such a depth, have undergone no greater lowering 

 of temperature, and may, therefore, if removed to a warmer temper- 

 ature, subsequently revive. 



The results of this paper suggest that similar experiments applied 

 to other cold-blooded animals would also lead to some modification 

 of present views. We hope especially to carry out some experiments 

 on fishes in this laboratory. 



Experimental Results. 



It is convenient to record the experiments according to their nature and results, 

 and not to deal with them chronologically. 



A . The general effect of freezing the frog. 



Experiment 1. Feb. 26th, 1913. Six frogs were placed together in a glass ves- 

 sel in the external atmosphere, at a temperature of — 25°C. After three-quarters 

 of an hour the external (skin) temperature of the frogs was -1°, and after one 

 hour this was unaltered. Two of the frogs were then removed to room temperature, 

 and examined immediately. They were quite rigid, and appeared to be frozen 

 solid. A wedge was cut out of the gastrocnemius of one frog, and the muscle (which 

 cut like clioe.se) was found to be frozen and full of ice. The abdomen and thorax 

 contents in this frog were not frozen, and the heart was beating. The second frog 

 recovered completely after two or three hours. 



At the end of one and a half hours the external temperature of the remaining 

 four frogs was — 3°C. Two more were removed and examined. They were found 

 to be frozen hard. The gastrocnemius of one frog was cut, and found to be full 

 of ice crystals. The abdomen contents appeared to be frozen. This frog recovered 

 completely in the anterior part of the body, but the hind limbs were dead. (This 

 phenomenon, as will be seen, was repeatedly observed, especially when the hind 

 limbs were frozen in a stretched condition ; it is easily explained by their relatively 



